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COVID-19 is now widely spreading around the world as a global pandemic. In this report, we estimate the global tendency of COVID-19 and analyze the associated global epidemic risk, given that the status quo is continued without further measures being taken.The results show that the global 0 , excluding China, is estimated to be 2.49 (95% CI: 2.15 -2.92). The United States, Germany, Italy and Spain have peak values over 100,000. According to dynamical model and cluster analysis, we category the globe into four type regional epicenters of the outbreak: Southeast Asia extending southward to Oceania, the Middle East, Western Europe and North America. Among them, Western Europe will become the major center of the outbreak. The peak values in Germany, Italy and Spain are estimated to be 105,903, 127,283 and 152,539, respectively. The United States is the country with the most serious outbreak trend. Based on the current control measures by Mar. 27, 2020, the peak value in the United States will reach 400,892. Above all, if the current control measures are maintained, the cumulative number of patients worldwide will be 1, 442,523 (95% CI: 1,052,981,440). We also estimated the diagnosis rate, recovery rate and infection degree of each country or region, and use clustering algorithm to retrieve countries or regions with similar epidemic characteristics. Different suggestions are proposed for countries or regions in different clusters.

The pandemic of coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to public concern worldwide. Although a variety of hypotheses about the hosts of SARS-CoV-2 have been proposed, an exact conclusion has not yet been reached. Initial clinical manifestations associated with COVID-19 are similar to those of other acute respiratory infections, leading to misdiagnoses and resulting in the outbreak at the early stage. SARS-CoV-2 is predominantly spread by droplet transmission and close contact; the possibilities of fecal–oral, vertical, and aerosol transmission have not yet been fully confirmed or rejected. Besides, COVID-19 cases have been reported within communities, households, and nosocomial settings through contact with confirmed COVID-19 patients or asymptomatic individuals. Environmental contamination is also a major driver for the COVID-19 pandemic. Considering the absence of specific treatment for COVID-19, it is urgent to decrease the risk of transmission and take preventive measures to control the spread of the virus. In this review, we summarize the latest available data on the potential hosts, entry receptors, clinical features, and risk factors of COVID-19 and transmission routes of SARS-CoV-2, and we present the data about development of vaccines.

Wireless power transmission (WPT) has great potential for charging electric vehicles. Constant voltage (CV) and constant current (CC) are two major types of battery charging modes. In this paper, we analyze the output characteristics of series–series (S-S) topology and double capacitances and inductances–series (LCCL-S) topology. Voltage gain variation is achieved in the LCCL-S compensation structure without additional components, and the system is still kept in resonant condition. A WPT experimental platform was also built and tested based on the theoretical analysis. When the load resistance is 300 Ω, a voltage gain of 0.7 or 2.22 is achieved for the LCCL-S with a compensating inductor of 100 μH or 33 μH, respectively. The experimental results fit the theoretical analysis. The CC/CV output characteristics and efficiencies of S-S and LCCL-S topologies in a wide load resistance range are also demonstrated. Moreover, zero voltage switch (ZVS) is also implemented in both two systems.

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